Different methods for reducing nitrogen oxide emissions in diesel vehicles are available, e.g., selective catalytic reduction (see, e.g., German Patent Application Nos. DE 197 28 343 C1, DE 10 2007 062 704 A1) or catalytic converters having a hydrocarbon trap (see, e.g., German Patent Application No. DE 197 55 600 A1).
A device and a method for measuring and indicating environmental contributions of a vehicle are described in German Patent Application No. DE 10 2007 048 130 A1. The device may also have an ecological driving-instructor function.